Field
The present invention relates to display devices comprising light-emitting diodes (LEDs) and films including luminescent nanocrystals such as quantum dots (QDs).
Background
In a backlight unit (BLU) of a display device (e.g., liquid crystal displays (LCDs)), LEDs are typically utilized as a light source. The LEDs may be arranged around the edge or perimeter of the display device and light emanating from the LEDs may enter a light guide plate (LGP), which distributes white light uniformly across the display device. White LED package designs have been optimized to enable high extraction efficiency and coupling efficiency into the LGP.
The BLUs often utilize phosphors, such as yttrium-aluminum-garnet (YAG) phosphors inside the LED package itself. Luminescent nanocrystals represent a new, alternative class of phosphors often used in configurations where the phosphor is placed external to the LED package. For example, luminescent nanocrystals may be embedded in a flexible film/sheet (e.g., quantum dot enhancement film (QDEF) supplied commercially from 3M Company, St. Paul, Minn. using quantum dots supplied by Nanosys, Inc, Milpitas, Calif.) that is placed above the LGP or the light source of the display device (see, e.g., U.S. Patent Publication Nos. 2010/0110728 and 2012/0113672, which are incorporated by reference herein in their entireties). In other examples, luminescent nanocrystals are encapsulated in a container, for example a capillary, which is placed between the LEDs and the LGP (see, e.g., U.S. Patent Publication No. 2010/0110728).
In current display devices, light may leak from the light sources of the BLU around the edges or perimeter of the display device and may appear as a hue of light around the sides of the display screen. This hue of light may be a problem when colored LEDs are used as light sources in the BLU. For example, FIG. 1 illustrates schematically a display device 100 having a blue hue of light 102 bordering around all sides (only sides 104 and 106 shown here) of a display screen 108 due to optical leakage from a blue LED light source in a BLU (not shown) of the display device 100. This blue hue of light bordering around the sides of the display screen 108 may interfere with the user's overall experience of the display device 100. For example, when there is a white background on the display device 100 and the display device 100 is used for reading electronic books, the blue hue of light at the edges fo the display screen can be an annoying distraction.